The present application relates generally to the field of power electronics and power switching devices. More particularly, the invention relates to a novel bus structure for use in such devices to reduce parasitic inductance.
Many applications exist for power electronic devices, including solid state switches. Such applications are found throughout the industry, and increasingly in non-industrial settings as well. In general, solid state switches may be used in a variety of circuitry, such as in inverter circuits that simulate desired waveforms, such as ac waveforms. In industrial drive applications, for example, power may be received from the power grid, converted to dc power, and then reconverted to controlled-frequency ac power by a switched inverter circuit. Devices of this type are used in conventional variable frequency drives, as well as in a variety of other products. Other applications include power converters, generators, power conditioning circuits, and so forth.
In conventional circuits based upon solid state power switches, the switches may be controlled to switch between conductive and non-conductive states extremely rapidly. Voltage spikes tend to occur, however, during turn-on stages of operation which can be detrimental to the operation of the circuitry. That is, as the solid state switching device is switched from a non-conducting state to a conducting state, such as to provide power to an output terminal, depending upon the configuration of the circuitry, large voltage spikes may occur which can cause damage to the switch and to other circuitry. In many cases, voltage spikes are caused by parasitic inductance in a dc circuit path, such as defined between elements of a dc bus used to convey power from a rectifier circuit to an inverter circuit. Similar problems exist both in single-phase circuitry and in three-phase circuitry.
While attempts have been made to improve performance of solid state switching circuits, additional improvement is necessary. For example, attempts have been made to place bus structures close to solid state switches to reduce the overall inductance of the bus. However, such attempts have not been entirely successful, and may involve complex mechanical designs with limited actual impact upon reducing the voltage spikes in operation.